Issue |
A&A
Volume 677, September 2023
|
|
---|---|---|
Article Number | A93 | |
Number of page(s) | 16 | |
Section | Numerical methods and codes | |
DOI | https://doi.org/10.1051/0004-6361/202346563 | |
Published online | 08 September 2023 |
Stellar metallicity from optical and UV spectral indices: Test case for WEAVE-StePS
1
INAF – Osservatorio Astronomico di Brera,
via Brera 28,
20121
Milano,
Italy
e-mail: fabio.ditrani@inaf.it
2
Università degli studi di Milano-Bicocca,
Piazza della scienza,
20125
Milano,
Italy
3
INAF – Osservatorio Astronomico di Capodimonte,
Via Moiariello 16,
80131
Napoli,
Italy
4
Centro de Astrobiología (CSIC-INTA),
Ctra de Ajalvir km 4, Torrejón de Ardoz,
28850,
Madrid,
Spain
5
INAF – Osservatorio Astrofísico di Arcetri,
Largo Enrico Fermi 5,
50125
Firenze,
Italy
6
Departamento de Física Teórica, Universidad Autónoma de Madrid,
28049
Madrid,
Spain
7
INAF – Osservatorio Astronomico di Padova,
Vicolo dell’Osservatorio 5,
35122
Padova,
Italy
8
Instituto de Física de Partículas y del Cosmos (IPARCOS), Universidad Complutense de Madrid,
28040
Madrid,
Spain
9
Isaac Newton Group of Telescopes, ING,
38700
La Palma (S.C. Tenerife),
Spain
10
Instituto de Astrofísica de Canarias, IAC,
Vía Láctea s/n,
38205,
La Laguna (S.C. Tenerife),
Spain
11
Departamento de Astrofísica, Universidad de La Laguna,
38206,
La Laguna (S.C. Tenerife),
Spain
12
School of Physics and Astronomy, University of Birmingham,
Birmingham
B15 2TT,
UK
13
INAF – Osservatorio di Astrofísica e Scienza dello Spazio,
Via P. Gobetti 93/3,
40129
Bologna,
Italy
14
INAF – IASF Milano,
via Bassini 15,
20133
Milano,
Italy
15
Dept. Physics, University of Oxford,
Keble Road,
Oxford
OX1 3RH,
UK
16
RAL, Space, Science and Technology Facilities Council,
Harwell, Didcot
OX11 0QX,
UK
17
Instituto de Astrofísica de Andalucía (CSIC),
PO Box 3004,
18080,
Granada,
Spain
18
Dipartimento di Fisica e Astronomia “G. Galilei”, Università di Padova,
vicolo dell’Osservatorio 3,
35122
Padova,
Italy
19
Kapteyn Astronomical Institute, Rijksuniversiteit Groningen,
Landleven 12,
9747
AD Groningen,
The Netherlands
20
SRON – Netherlands Institute for Space Research,
Landleven 12,
9747
AD Groningen,
The Netherlands
21
Dipartimento di Fisica “E.R. Caianiello”, Università degli studi di Salerno,
Via Giovanni Paolo II 132,
84084
Fisciano (SA),
Italy
22
Instituto de Astronomía y Ciencias Planetarias de Atacama (INCT), Universidad de Atacama, Copayapu
485,
Copiapó,
Chile
23
Institute of Astronomy, University of Cambridge,
Madingley Road,
Cambridge
CB3 0HA,
UK
Received:
29
March
2023
Accepted:
20
July
2023
Context. The upcoming generation of optical spectrographs on four meter-class telescopes, with their huge multiplexing capabilities, excellent spectral resolution, and unprecedented wavelength coverage, will provide high-quality spectra for thousands of galaxies. These data will allow us to examine of the stellar population properties at intermediate redshift, an epoch that remains unexplored by large and deep surveys.
Aims. We assess our capability to retrieve the mean stellar metallicity in galaxies at different redshifts and signal-to-noise ratios (S/N), while simultaneously exploiting the ultraviolet (UV) and optical rest-frame wavelength coverage.
Methods. The work is based on a comprehensive library of spectral templates of stellar populations, covering a wide range of age and metallicity values and built assuming various star formation histories, to cover an observable parameter space with diverse chemical enrichment histories and dust attenuation. We took into account possible observational errors, simulating realistic observations of a large sample of galaxies carried out with WEAVE at the William Herschel Telescope at different redshifts and S/N values. We measured all the available and reliable indices on the simulated spectra and on the comparison library. We then adopted a Bayesian approach to compare the two sets of measurements in order to obtain the probability distribution of stellar metallicity with an accurate estimate of the uncertainties.
Results. The analysis of the spectral indices has shown how some mid-UV indices, such as BL3580 and Fe3619, can provide reliable constraints on stellar metallicity, along with optical indicators. The analysis of the mock observations has shown that even at S/N = 10, the metallicity can be derived within 0.3 dex, in particular, for stellar populations older than 2 Gyr. The S/N value plays a crucial role in the uncertainty of the estimated metallicity and so, the differences between S/N = 10 and S/N = 30 are quite large, with uncertainties of ~0.15 dex in the latter case. On the contrary, moving from S/N = 30 to S/N = 50, the improvement on the uncertainty of the metallicity measurements is almost negligible. Our results are in good agreement with other theoretical and observational works in the literature and show how the UV indicators, coupled with classic optical ones, can be advantageous in constraining metallicities.
Conclusions. We demonstrate that a good accuracy can be reached on the spectroscopic measurements of the stellar metallicity of galaxies at intermediate redshift, even at low S/N, when a large number of indices can be employed, including some UV indices. This is very promising for the upcoming surveys carried out with new, highly multiplexed, large-field spectrographs, such as StePS at the WEAVE and 4MOST, which will provide spectra of thousands of galaxies covering large spectral ranges (between 3600 and 9000 Å in the observed frame) at relatively high S/N (>10 Å−1).
Key words: galaxies: evolution / galaxies: formation / galaxies: stellar content
© The Authors 2023
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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